Method for operating a power supply circuit in an inverter for driving an electric machine, computing unit, power supply circuit in an inverter and inverter

Abstract

A power supply circuit in an inverter for driving an electrical machine has a high-voltage branch with a high-voltage level and a low-voltage branch with a low-voltage level, the high-voltage level being higher than the low-voltage level, the high-voltage branch being connected to the low-voltage branch via an operating DC/DC converter, the low-voltage branch having a supply branch and a mains branch, the high-voltage branch being connected to the mains branch via a discharge DC/DC converter. A method for operating the power supply circuit includes, in a first operating mode conducting current from the high-voltage branch via the operating DC/DC converter into the supply branch, and in a second operating mode, conducting current from the high-voltage branch via the discharge DC/DC converter into the mains branch.

What is claimed is: 
     
         1 . A method for operating a power supply circuit ( 100 ,  200 ) in an inverter ( 1 ) for driving an electrical machine ( 500 ), the power supply circuit ( 100 ,  200 ) in the inverter ( 1 ) comprising:
 a high-voltage branch ( 110 ) with a high-voltage level,   a low-voltage branch ( 120 ) with a low-voltage level, the low-voltage branch ( 120 ) having a supply branch ( 120   a ) for distributing current to components of the inverter ( 1 ) and a mains branch ( 120   b ) for connection to a low-voltage network,   an operating DC/DC converter ( 10 ), which is connected on the one hand to the high-voltage branch ( 110 ) and on the other hand to the low-voltage branch ( 120 ),   a discharge DC/DC converter ( 20 ), which is connected on the one hand to the high-voltage branch ( 110 ) and on the other hand to the mains branch ( 120   b ),   the high-voltage level being higher than the low-voltage level,   wherein the method comprises the steps of:
 in a first operating mode, conducting current from the high-voltage branch ( 110 ) via the operating DC/DC converter ( 10 ) into the supply branch ( 120   a ), wherein no current is conducted from the high-voltage branch ( 110 ) via the discharge DC/DC converter ( 20 ) into the mains branch ( 120   b ), 
 in a second operating mode, conducting current from the high-voltage branch ( 110 ) via the discharge DC/DC converter ( 20 ) into the mains branch ( 120   b ). 
   
     
     
         2 . The method according to  claim 1 , wherein the operating DC/DC converter ( 10 ) and the discharge DC/DC converter ( 20 ) are the same DC/DC converter. 
     
     
         3 . The method according to  claim 1 , comprising, in a third operating mode, conducting current from the mains branch ( 120   b ) via the discharge DC/DC converter ( 20 ) into the high-voltage branch ( 110 ). 
     
     
         4 . The method according to  claim 1 , wherein a discharge circuit ( 30 ) is used, the discharge circuit ( 30 ) comprising a mains branch disconnector ( 31 ) for connecting and disconnecting the mains branch ( 120   b ) to and from the discharge DC/DC converter ( 20 ), and/or a supply branch disconnector ( 32 ) for connecting and disconnecting the supply branch ( 120   a ) to and from the operating DC/DC converter ( 10 ). 
     
     
         5 . The method according to  claim 4 , wherein in the first operating mode the supply branch disconnector ( 32 ) is closed and the mains branch disconnector ( 31 ) is open. 
     
     
         6 . The method according to  claim 5 , wherein in the second operating mode the mains branch disconnector ( 31 ) and the supply branch disconnector ( 32 ) are closed. 
     
     
         7 . The method according to  claim 5 , wherein in the second operating mode the mains branch disconnector ( 31 ) is closed and the supply branch disconnector ( 32 ) is open. 
     
     
         8 . The method according to  claim 7 , wherein the mains branch disconnector ( 31 ) is closed first and the supply branch disconnector ( 32 ) is opened with a delay. 
     
     
         9 . The method according to  claim 1 , wherein in the second operating mode the current flowing from the high-voltage branch ( 110 ) via the discharge DC/DC converter ( 20 ) into the mains branch ( 120   b ) is regulated to a set current intensity. 
     
     
         10 . The method according to  claim 9 , wherein the current is controlled by controlling a semiconductor switch ( 343 ,  31 ). 
     
     
         11 . The method according to  claim 1 , wherein in the second operating mode the discharge DC/DC converter ( 20 ) is operated with constant voltage at the mains branch ( 120   b ). 
     
     
         12 . A computing unit ( 400 ) adapted to perform a method according to  claim 1 . 
     
     
         13 . A power supply circuit ( 100 ,  200 ) in an inverter ( 1 ) for driving an electrical machine ( 500 ), the power supply circuit ( 100 ,  200 ) comprising
 a high-voltage branch ( 110 ) with a high-voltage level,   a low-voltage branch ( 120 ) with a low-voltage level, the low-voltage branch ( 120 ) having a supply branch ( 120   a ) for distributing current to components of the inverter ( 1 ) and a mains branch ( 120   b ) for connection to a low-voltage network,   an operating DC/DC converter ( 10 ), which is connected on the one hand to the high-voltage branch ( 110 ) and on the other hand to the low-voltage branch ( 120 ),   a discharge DC/DC converter ( 20 ), which is connected on the one hand to the high-voltage branch ( 110 ) and on the other hand to the mains branch ( 120   b ),   wherein the low-voltage branch ( 120 ) is arranged to supply components ( 121 ,  115 ) of the inverter with energy,   the power supply circuit ( 100 ,  200 ) further comprising a computing unit ( 400 ) for performing a method comprising the steps of:
 in a first operating mode, conducting current from the high-voltage branch ( 110 ) via the operating DC/DC converter ( 10 ) into the supply branch ( 120   a ), wherein no current is conducted from the high-voltage branch ( 110 ) via the discharge DC/DC converter ( 20 ) into the mains branch ( 120   b ), 
 in a second operating mode, conducting current from the high-voltage branch ( 110 ) via the discharge DC/DC converter ( 20 ) into the mains branch ( 120   b ). 
   
     
     
         14 . The power supply circuit ( 100 ,  200 ) according to  claim 13 , further comprising a discharge circuit ( 30 ) which can be switched in such a way that the high-voltage branch ( 110 ) is either electrically connected to the mains branch ( 120   b ) via the discharge DC/DC converter ( 20 ) or is electrically isolated from the mains branch ( 120   b ). 
     
     
         15 . The power supply circuit ( 100 ,  200 ) according to  claim 13 , wherein the discharge circuit ( 30 ) is switchable such that the high-voltage branch ( 110 ) is either electrically connected to the low-voltage branch ( 120 ) via the operating DC/DC converter ( 20 ) or is electrically isolated from the low-voltage branch ( 120 ). 
     
     
         16 . The power supply circuit ( 100 ,  200 ) according to  claim 13 , further comprising a current intensity determining device ( 34 ) with a semiconductor switch ( 343 ) for regulating a current intensity from the high-voltage branch ( 110 ) into the mains branch ( 120   b ). 
     
     
         17 . An inverter ( 1 ) comprising a power supply circuit ( 100 ,  200 ) according to  claim 13  and an inverter circuit ( 115 ), the inverter circuit ( 115 ) comprising a number of semiconductor switches to be driven by means of drive signals, further comprising low-voltage terminals (B+, B−) adapted to be connected to a low-voltage network of a vehicle, high-voltage terminals (HV+, HV−) adapted to be connected to a high-voltage network ( 1 ) of the vehicle, and machine terminals (HV−, HV−) adapted to be connected to stator windings of the electric machine ( 500 ).